GAS-PHASE AND SURFACE-REACTION MECHANISMS IN MOCVD OF GAAS WITH TRIMETHYL-GALLIUM AND ARSINE

A kinetic model for metalorganic chemical vapor deposition of GaAs from trimethylgallium and arsine has been developed. From the large number of gas-phase and surface reactions that might in principle occur, we have identified a reduced set that preserves key features observed in experimental studies. The proposed mechanism involves 15 gas-phase species participating in 17 gas-phase reactions and 9 surface species participating in 26-28 surface reactions depending on the crystallographic orientation of the substrate. The orientations considered in this study are the (110), the (100)-misoriented As-stabilized, and the (111)-Ga surface. The kinetic model also includes a reaction scheme for carbon incorporation based on two-site adsorption of carbene containing gallium species. The detailed reaction mechanism provides insights into the relative importance of different reaction pathways. A sensitivity analysis indicates that the growth rate predictions strongly depend on surface reactions but not on the details of the gas-phase chemistry. However, the complete reaction mechanism is critical to the simulation of carbon incorporation. The model predicts quantitatively decomposition data for the metalorganic precursor in hot isothermal tubes. In addition, it reproduces observed trends in GaAs growth behavior and carbon incorporation measurements.